In the ADAPT study, pCR rates were 41.5% and 15.1% in patients with HER2+ HR+ breast cancer receiving concomitant HT with 12-week T-DM1 and trastuzumab, respectively [20], suggesting improved efficacy of anti-HER2 therapy without any detrimental effects with concomitant HT. This evidence concerns the gene ERBB2 and breast cancer.